Science
NASA's solar observatory to improve forecasts of space weather
Science | July 14, 2008 12:46:46 PM IST
With assistance from the National Institute of Standards and Technology (NIST), NASA's Solar Dynamics Observatory (SDO) will peer deep inside the sun, with the aim of improving forecasts of space weather. About six times each minute of every hour for at least five years, the soon-to-be launched NASA satellite will measure the sun's quirky-and sometimes stormy-output of extreme ultraviolet (EUV) light. To ensure that this solar stake-out yields data useful for understanding the weather in space and its earthly consequences, researchers at the National Institute of Standards and Technology (NIST) are helping a NASA team prepare for annual rocket-borne check-ups of key instruments aboard the Solar Dynamics Observatory. From one multi-year solar cycle to the next, the amount of ultraviolet radiation generated by the sun can change as much as tenfold. On shorter time scales-during, for example, a violent solar flare-ultraviolet output can jump by a factor of 1,000 in a matter of minutes. EUV light is highly energetic. It is absorbed by the Earth's upper atmosphere, ionizing gases and creating electric currents that form the inner edge of the Earth's magnetosphere. Changes in the sun's magnetic field driven by the solar wind in turn affect the Earth's atmospheric electric currents and magnetic fields, and can cause such disruptive effects as wreaking havoc with the electric power grid of an entire nation. In addition, the ionization of atmosphere gases by EUV and X-ray irradiation disrupts the high-frequency radio communication and decreases the accuracy of GPS systems. Related phenomena can change the density of the upper atmosphere, increase the drag on satellites in low-Earth orbit, and knock them out of orbit. To better understand the origins and impacts of EUV phenomena, the SDO's three onboard experiments will make nearly continuous observations of changes in the sun's magnetic field, solar-flare and other activity on the surface and in the interior, and energy outputs. According to NASA, the experiment will produce enough data on solar EUV output to fill one compact disc every 36 seconds. In October, a few months before the SDO's tentatively scheduled launch, the NASA team will perform a dry run of the rocket-science equivalent of telemedicine. A rocket will carry duplicates of instruments built for SDO's EUV Variability Experiment, or EVE. If only for a minute or two, the duplicate devices will take measure of the Sun's EUV emissions. Data gathered during the brief outing will enable NIST to complete its characterization of the EUV spectrophotometer, which detects EUV emissions at several specific wavelengths, including those associated with solar flares. (ANI)
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